Stencil and backing unit



C. K. HEASLEY STENCIL AND BACKING UNIT Filed Dec. 15, 1944 INVENTOR.

y f MWMW Patented Jan. 5, 1954 STENCIL AND BACKING UNIT Charles K.Heasley, St. Paul, Minn., assignor to Minnesota, Mining & ManufacturingCompany, St. Paul, Minn., a corporation of Delaware Application December15, 1944, Serial N 0. 568,313

6 Claims.

This invention relates to the art of forming stencils such as those usedin duplicator machines and particularly to a stencil and compositebacking sheet wherein a surface composed of a multiplicity of minute,substantially spherical protuberances affords a substantially uniformlylevel but discontinuous support for the stencil during the typing andother stencilizing operations.

Most of the commercial stencil sheets for use in duplicator machineshave been composed of thin tissue paper, such as Yoshino, coated with awax or other pressure displaceable composition to render them imperviousto ink. During the stencilizing of such sheets it has been customary toplace a cushion of tissue paper, either plain or coated, in contact withthe back face of the sheet and to back the cushion in turn with asmooth, hard surfaced film or sheet of paper. The group of sheets thusarranged is placed in a typewriter which is operated to cause the typeto strike the stencil sheet and thereby dislodge the wax or otherink-impervious substance from the areas of the impressions. From theseareas the inkimpervious substance is either displaced laterally or iscaused to adhere to the cushion, leaving the stencil characterspermeableto ink.

By the present invention I obviate a number of difiiculties which areattendant upon the use of such backing materials. Due to the relativelyirregular fibrous consistency of the cushion sheet the resulting stencilcharacters are not uniformly clear and the quality of the worksubsequently performed by the duplicator machine through the stencil isalso relatively irregular. There is also atendency for the type to cutthrough the fibers of the stencil sheet where there is a continuous,relatively hard surfaced backing, thus completely separating the areasbounded by the closed loops of characters such as a, e, 0, etc. The waxor other coating for stencils of this kind is usually dyed a dark colorand enough of the displaced colored material remains on the areas of theimpressions to make the stencil characters poorly legible until afterthe cushion carrying the dislodged material has been separated from thestencil sheet. Consequently the stencil is not easily legible forproof-reading without removal from the typewriter and this makes itrelatively diflicult to correct errors. Further difiiculties aresometimes encountered when it is attempted to write or draw with astylus on the stencil sheet because of the softness of both this sheetand the cushion tissue. 7

It is an object of the present invention to provide a stencil with animproved backingin which a multiplicity of substantially uniform,smoothly substantially uniform size.

(Cl. lobe-128.2)

2 rounded segments are utilized to support the sheet during thestencilizing operation.

. A particular object is to produce more clearly defined stencilcharacters by providing a stencil backing having directly opposed toeach type face a multiplicity of substantially uniformly spaced, smooth,spheroidal protuberances in contact with the stencil sheet and havingrecesses between the several protuberances into which all of thepressure-displaceable, ink-impervious material from the stencil willpass readily in the stencilizing operation,

Another object is to provide a stencil backing of such durable characterthat it may be used a large number of times, having durable, smooth,

spheroidal glass or vitreous protuberances from which the wax or othersubstance displaced from the stencil sheet may be readily removed by theapplication of a solvent. 3

A further object is to provide a stencil backing from which sufficientlight is reflected through the porous areas of the impressions to renderthe stencil characters easily legible without separation of the stencilsheet from the backing.

Other objects are to provide a stencil backing which minimizes thecutting of the stencil fibers, minimizes damage to the type during thecutting operation, facilitates free-hand writing and drawing on thestencil sheet and affords a durable, permanent record of the documentreproduced on the stencil.

My composite backing has a facing composed of a single layer of hard,globular particles of These particles are securely bonded individuallyto a flexible backing by a suitable adhesive. To insure an adequate bondthe adhesive is carefully selected for its resistance to impact as wellas its adhesion to the particles and backing sheet. Care is exercised tosubmerge each spheroidal particle in the adhesive to a depth notexceeding one-half its diameter and preferably between 30% and 50% ofits diameter. This affords recesses of adequate capacity between theprotruding segments to receive the wax or other material dislodged fromthe stencil. It will thus be evident that a large number of the recessesextend beneath the overhanging peripheries of the spheroidal particles.The facing layer is preferably composed of particles of one of thesmaller sizes, for example, bead sizes No. 15 to No. 19. Equivalentaverage particle diameters are approximately as follows:

Bead size: Diameter in microns 15 .58 17 .43 19 .24.

Facing particles of these sizes, ranging from approximately .001 inch to.003 inch, are particularly adapted for use where the stencilizing is tobe performed on a typewriter having type faces ranging from about .01 to.015 of an inch in width.

Excellent results have been obtained by forming the globular particlesfor my .purpose from a lime soda glass, such as that commonly used inthe manufacture of glass containers and window panes. Other materialshaving suitable surface qualities and adequate resistance to crushing;for my purpose are metals, metal alloys, ceramic material and.synthetic resins. As the support or backing for the globular particlesa' pa-per maybe used, such as wood pulp or rope paper of twenty pound orheavier weight, aseventy pound paper being preferred for use with mostwax coated stencil sheets. It will be understood that such Weightdesignation represents the weight of a :ream of the paper,'i. e.,480sheets-of size 24 inches by 36 inches. Other materials which may besubstituted for the "paper backin are sheets of rubber or rubberderivative "or-a suitable synthetic resin film.

Where the-composite sheet'is to be used with a stencil sheet impregnatedwith a wax or other material of dark color, -I provide either a backing'or an adhesive containing a white pigment or of a'light color and I use.clear or light colored glass :or white particles'as a facing, thusaffording maximum contrast between the dark wax or other substancedisplaced "and the backing to which such substance adheres. dark backingor dark adhesive is supplied for use with white or light tinted stencilsheets. This improves the legibility of the stencil character when readagainst the backing for the detection of errors and also the legibilityof the characters on the backing when the latter is used as a permanentrecord sheet.

The adhesive may comprise a suitable glue or a rubber or syntheticelastomer composition, or a thermo-setting synthetic resin, such asphenolaldehydes, urea-formaldehyde, melamine aldehyde, thiourea-formaldehyde, alkyd resins, etc., or mixtures of such resins or asuitable thermoplastic resin. Most highly plasticized resins andunmodified starches have insufii'cient bonding strength for my purposes.'The adhesive must be chemically "inert with respect to the stencilsheet with which it may be in contact for long periods of time.

In cases where the backing is to be used repeatedly its componentscomprising the supporting sheet, adhesive and globular particles must bechemically inert with respect to the solvents that may be used inremoving the wax or other deposits from previous sten'ciling operations.For example, with wax coated stencils ether or alcohol may be applied tothe glass sphere .coated backing to remove deposits of wax therefrom andin this case the adhesive bond and supporting sheet or film must beinert to these solvents.

My improved stencil backing material may be prepared by either ofseveral known methods which have been employed in the manufacture ofcoated abrasive material. For example, the solid globular particles maybe dropped upon a flexible backing 'upon which there is a surfacecoating of a suitable adhesive of the requisite thickness and the excessparticles may then be removed. As the next step, before the adhesive hasset, the coated web may be passed between accurately spaced nip rollswhich level the tops of the globular particles and submerge them'to ;orby spraying with a sizing solution, or by any other suitable means.

:Other methods -of applying solid particles to a backing which may beadapted to the manufacture of my composite stencil backing are thosedescribed generally in Carlton Patent No. 2,318,570. Such methods areparticularly adapted to secure uniform spacing of the particles byreason of the dispersing action resulting from the electrical chargesimposed upon the particles. "To accurately level the "tops of allparticles and to submerge their lower portions to the required depth inadhesive the freshly coated web may then be passed beneath a niprolliwhich I is accurately spaced from another machine element in:contact with the fle'x ible backing so that the spacing of thesemachine elements corresponds to the overall thickness of the product.Finally the globular particles are retained at this controlled depth inthe adhesive and with their tops uniformly level during the setting-cf:the adhesive.

Where, as is usually the case, closely spaced point for contact with thestencil are desirable, care is taken to crowd the particles togetherleaving only a thin film o'f 'a'dhesi'vebetweeh their adjoiningperipheries. The resulting product possesses the highest degree ofuniformity because the number .of :points of contact afforded by theprotruding spherical segments-Over a given area is determined by theaccurate grading of the particles themselves, for size.

To illustrate an exemplary embodiment of the invention, and not to limitit, reference is had to the accompanying drawing in which:

Figure 1 is 'a plan view showing my improved stencil sheet and backingunit;

Fig. :2 is a magnified plan view showing a fragmen-tary portion of thestencil sheet and backing on which a type impression has been made;

.Eig. :3 -is a further magnified section takenpn the line 3-3 of Fig. 2and illustrating the coaoperative relationship between the stencil and:backing, as well as prefer-red details of the backmg, and

Fig. 4 is a fragmentary plan view showing a fragment of the face of thebacking on which 'wax or other ink-impervious material from a stencilhas been impressed by a type, also on an enlarged scale.

the drawing a stencil sheet, indicated 'generally by the numeral 5, isshown in assembled relation to my improved backing, indicated generallyby the numeral "These elements may be joined together in the usualmanner by a narrow band of adhesive 3 extending along the upper marginof the sheet 5, in spaced relation to the upper edge 'of the backing 16,thereby leaving a margin 8 of the backing 6 which projects to facilitatethe fastening of the stencil sheet to its support in the duplicatormachine. Keyhole shaped perforations 9 in the margin 18 are provided toreceive lugs on the cylinder or other stencilysupporti-ng element of themachine. To

facilitate the necessary separation of the impression part of thebacking B from its margin 8 aline of perforations If? is formed therein,be-

low and adjacent to the band of adhesive I.

As shown in detail in Fig. 3, my improved backing sheet has a facingcomposed of a single layer of minute, spheroidal particles II which aresecured by means of a coat of adhesive I2 to a flexible supporting sheetI3. As hereinbefore described, the particles II preferably compriseininute spherical or spheroidal glass particles of substantially uniformsize, substantially uniformly distributed to afford a level butdiscontinuous surface for contact with the stencil sheet 5. Each ofthese particles is submerged in the adhesive I2 to a depth of from to50% of its diameter so-that recesses are provided between theirprotruding segments of sufficient capacity to receive all of theink-impervious coating material that is to be displaced from the stencilsheet 5 over the areas of the impressions. The stencil sheet 5 has atissue paper base i4, composed of long fibers and coated on its faceadjacent the particles. II with an ink impervious material I5 which maybe a wax, a mixture of waxes or other suitable pressure displaceablesubstance.

To prepare the stencil sheet 5 to duplicate typewritten matter theassembly comprising this sheet and the backing 6, shown in Fig. 1, isplaced on the platen of a typewriter'as for ordinary typing and, withthe inking mechanism inoperative, the machine is operated in the usualmanner to type the subject-matter on the uncoated face of the stencilsheet. During this operation the keys apply suflicient pressure upon theareas of the type characters to displacethe ink-impervious material I5from the fibrous base l4 into the recesses between the protrudingsegments of the spherical particles II. This is illustrated in detail inFig. 3'wherein a fragmentary portion of a type is indicated at I6 incross section and greatly magnified. A face Isa of the type is shownwithdrawn slightly from the area of the impression and is representativeof the width, usually .01 to .015 inch, ofthe ordinary type facesapproximately to the same scale as that of the backing 6 which is alsoshown in this view. Pressure thus applied causes the coating material I5to be displaced into the recesses between the globular particles II, asindicated at IT, leaving the fibrous stencil area I 8 pervious to ink.In Fig. 2 this pervious area I8 of one of the type characters, viz.: theletter t, is shown in plan view and in Fig. 4 the displaced material I"!is indicated on the sphere coated backing sheet 6.

Uniformly well defined stencil characters are obtained by reason of thefact that the ink-impervious material is allowed to escape from theentire area of each impression into the uniformly distributed recessesof adequate capacity between the rounded protuberances of the facingparticles. This will be understood when it is considered that the faceIlia of each type character is opposed by a large number of minute,smoothly rounded protuberances which support the fibers of the stencilbase I4 without cutting them, while directing the displaced material I5into the immediately adjoining recesses. Damage to the typewriter keysis prevented not only by the cushioning effect of the stencil materialbut also by the smooth, nonabrasive character of the protuberances andthe large number of them which oppose each type face,

My improved backing coacts with the stencil sheet in a similar manner toproduce clearly defined, pervious areas when the impressions are made bya stylus, as in free hand writing and drawing on the sheet 5. In thiscase the smoothly rounded, hard surfaced, protuberances formed by theparticles I I afford a support which allows the stylus to glide smoothlyover the stencil With-,- out severing or detrimentally disturbing theflbers comprising the base I4.

As long as the backing remains in contact with the stencil the workthereon is clearly legible by reason of the fact that my preferredtransparent glass particles are excellentreflectors of light which coactwith the white or light colored back-:- ing to illuminate the perviousareas formed by the impressions, notwithstanding the presence of thenetwork of fibers remaining in these areas. Moreover, legibility isimproved even when the spheroidal particles are composed of opaquematerial of a color which contrasts with that of the stencil sheetbecause the smoothly rounded pro tuberances deflect the displaced waxinto the adjoining recesses which are uniformly distributed and havesuificient capacity to insure exposure of the tops of the particles incontact with the fibrous network of the stencil. Consequentlyproof-reading and the making of corrections without removing the stenciland backing from the typewriter is facilitated by the present invention.

The displacement of the wax or other ink-impervious substance into therecesses of the backing 8 is so uniform and complete that this productis adapted to constitute a clearly legible, permanent record of thesubject-matter impressed on the stencil. It is more durable than mostrecord papers and ordinary rubbing of the sphere coated face does notremove or otherwise affect the legibility of the impressed deposits. Inthe event that the backing is not needed as a permanent record, asubstantial saving in the cost of the duplicating may be effected byrepeated use of the same sphere coated backing sheet. To remove previousdeposits it is only nec-i essary to apply a solvent for the wax or otherdeposited substance by suitable mean such as a cloth or brush. Suchcleaning is greatly facilitated where the surface to be cleaned iscomposed of my preferred, smooth, spheroidal protuberances of glass orof other globular particles which are similarly devoid of abrasivepoints and edges.

The discontinuous nature of the surface of my improved stencil backingaffords a multitude of minute recesses between the adjacent sphericalparticles and when the stencil sheet is hit by the type face orotherwise impressed as by a stylus these recesses serve to accommodatethe fibers of the stencil sheet and to prevent the cutting of thesefibers, thus eliminating the cutting out of closed loops of characterssuch as the letter O, which is one of the above noted defects of theprior constructions utilizing a smooth backing sheet. Accordingly theuse of my improved stencil backing not only results in improved stencilswhen used with stencil sheets of special long fiber tissue paper, butalso make possible the use as a stencil sheet of less expensive tissuepaper with shorter fibers which would not be satisfactory for use withthe smooth continuous surfaces of the backing sheets previously used.

What I claim is:

1. In combination, a stencil sheet upon which pervious areas may beformed by the application of pressure and without perforating the sheetand 4a aback-mg ifor said sheet comprising a meniplicity er minuteglobular particles of substanmay funisiorm :si'ze having roundedsegirient's protruiimg in contact with said sheet and in relation to:each other, a flexible support in said particles and an adhesivebonding said particles to said support, said. particles be ing submergedin the ia'dh'esive to a depth knot exceeding :ene ha lf their:diameters.

2. in combination, :a stencil sheet upon which pewious areas may beformed by the application 56f pressure and a :backing for said "sheetcom"- pixising a multipli'city of minute globular, glass narticlesrl'iaving :rou'n'ded segments protruding in contact with said sheet and.in spaced relation to'each other, "afiording a substantially level butdiscontinuous -supporting surface for saidstencil sheet, :a flexiblesupport \for said particles and an adhesive bonding said particles "tosaid support.

3. combination, a stencil sheet upon which penvious areas may be formedthe application of pressure and :a backing for said sheet comprising :asingle layer of substantially spherical particles "of substantiallyuniform size, the diameters :of which do not exceed .-003 inch and eachhaving a rounded segment protruding in contact with the stencil sheet,affording a substantially level but discontinuous supporting :surfaceifor sa-i'd stencil sheet, a flexible support for said particles and anadhesive @bonding said particles l-to said support.

4.;11-1 combination, a-stencil sheet composed of a fibrous base carryingpressu-re-displaceahle costing ia-nd a backing for 'said shee'tcomprising 2. single compact layer of spheroidal particles ofsubstantially uniform size having smooth, rounded segments:pr'ot-rud-ing in contact with said sheet, affording a substantiallylevel but discontinuous supporting surface for said stencil sheet, thediameters of said particles being not 'laaiger than @093 inch, =aflexible support for said particles and an adhesive bonding saidparticles to said support and submerging them to a depth notexceedingone-half their diameters, the space between mmtruding segmentsof said particles being adaiotei'l to receive the coating displaced fromsaid sheet by steno'il i'zin'g pressure.

'5. In combination, a stencil sheet composed of a fibrous bas'e earry mga coating of ressure- 'displaceable wax and a backing for said sheetcomprising a single compact layer or spheroidal glass particles ofsubstantially uniform sizeflea'ch having a sm'ooth, rounded seg r'nen'tprotruding in oontact with the wax "coated surface of said sheet, "aflexible support for said particles and an adhesive bondin'g 's'a-idparticles to sai'd support and submergin'g them to a depth of from 30%to or their diameters, the space between protruding segments "of saidparticles having capacity sufficient to contain allof the was displaoedfrom said sheet by stenc'iliz'ing pressure.

'6. A stem-d1 sheet assembly comprising a type and styms i mpfESSible=st'enei1-sheetnaving a. base tissue of interlaced fibres impregnatedwl'th a p'ressui e dis'pl'aceable coating, and a backing for saidstencil sheet having one surface foiimed by a =layer of small, hard,elastic-bodies set in spaced relati'onin ='a :plasti'cally deformableadhesive, said bodies having rounded projections adapted to oontaotthe'stencil sheet and defining inter'sp'ac'es for reception ofthefibr'es and oi coating material expressed during 's'tenciliza'tion.

*CHARLES 'K. References Cited In the file of This patent UNITED STATESPATENTS

